195821309 has 2 divisors, whose sum is σ = 195821310. Its totient is φ = 195821308.

The previous prime is 195821267. The next prime is 195821347. The reversal of 195821309 is 903128591.

It is an a-pointer prime, because the next prime (195821347) can be obtained adding 195821309 to its sum of digits (38).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 161925625 + 33895684 = 12725^2 + 5822^2 .

It is a cyclic number.

It is not a de Polignac number, because 195821309 - 2¹⁶ = 195755773 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (195821359) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 97910654 + 97910655.

It is an arithmetic number, because the mean of its divisors is an integer number (97910655).

Almost surely, 2^195821309 is an apocalyptic number.

It is an amenable number.

195821309 is a deficient number, since it is larger than the sum of its proper divisors (1).

195821309 is an equidigital number, since it uses as much as digits as its factorization.

195821309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19440, while the sum is 38.

The square root of 195821309 is about 13993.6167233493. The cubic root of 195821309 is about 580.7019928583.

The spelling of 195821309 in words is "one hundred ninety-five million, eight hundred twenty-one thousand, three hundred nine".